Micromechanical modeling of the elastic properties of semicrystalline polymers: A three‐phase approach

The mechanical performance of semicrystalline poly- mers is strongly dependent on their underlying microstructure, consisting of crystallographic lamellae and amorphous layers. In line with that, semicrystalline polymers have previously been modeled as two and three-phase composites, consisting of a crys- talline and an amorphous phase and, in case of the three-phase composite, a rigid-amorphous phase between the other two, hav- ing a somewhat ordered structure and a constant thickness. In this work, the ability of two-phase and three-phase composite models to predict the elastic modulus of semicrystalline polymers is investigated. The three-phase model incorporates an internal length scale through crystalline lamellar and interphase thick- nesses, whereas no length scales are included in the two-phase model. Using linear elastic behavior for the constituent phases, a closed form solution for the average stiffness of the inclusion is obtained. A hybrid inclusion interaction model has been used to compute the effective elastic properties of polyethylene. The model results are compared with experimental data to assess the capabilities of the two- or three-phase composite inclusion model. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2173-2184, 2010